Rickard, Helen;
(2025)
Investigating the microbial communities within hospital sinks.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Healthcare associated infections (HCAI) are a major threat to both patients and healthcare systems worldwide due to poor patient outcomes and high financial costs. Hand washing is widely reported as the single most effective way of reducing HCAI, however, hospital sinks are reservoirs of potential pathogens and have been implicated in several serious infection outbreaks. Organisms associated with sink biofilms, such as Pseudomonas aeruginosa and Klebsiella pneumoniae, have been linked to sink related HCAI. Little is known, however, about other Pseudomonas species which colonise the same areas in terms of presence, virulence, or antimicrobial susceptibility. The work in this thesis was performed with the aim of determining the effect patients have on the sink microbiome. Additionally, to characterise the sink Pseudomonas population in terms of virulence factor production, and to investigate the impact of routine cleaning and disinfection on individual sink bacteria. A total of 106 bacterial isolates were recovered from 62 sinks across two new wards at Great Ormond Street Hospital before and after the wards were opened to patients. Findings indicated changes in the organisms found in sinks before and after wards opened to patients, 71% of isolates were recovered after the wards opened and increased numbers of human- and disease-associated organisms were found at this timepoint. Additionally 91% of drug-resistant organisms were recovered after the wards opened. The ability of non-aeruginosa Pseudomonas isolates to produce virulence factors typically associated with P. aeruginosa was established, with non-aeruginosa strains able to produce all tested isolates other than gelatinase. Strain and product specific responses to exposure to products used for cleaning and disinfection of sinks were also identified, with a P. monteilii isolate showing greater phenotypic responses compared to the P. aeruginosa and K. pneumoniae isolate investigated. Responses in the test organisms were not likely to be clinically significant but with the most notable changes to disinfectant tolerance, antimicrobial susceptibility, and biofilm production occurring following 24 hours exposure to a benzalkonium chloride containing product. This work aims to enhance the understanding of sinks as a source of HCAI to improve infection prevention policies and patient outcomes.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Investigating the microbial communities within hospital sinks |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10207691 |
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